Technique and system for lateral lumbar spine fusion

ABSTRACT

A lumbar spine fusion system includes a probe and a retractor blade. The probe includes a shaft, a pointed tip, and a collar. The pointed tip is configured to puncture tissue in a disk space of a disk and anchor the probe to the tissue. The collar is configured to act as a stop to control a distance through which the shaft of the probe traverses the tissue. The retractor blade includes an end portion and a slot. The slot is configured to receive at least a portion of the shaft of the probe. At least a portion of the end portion is configured to rest upon one or more of the disk and the collar when the retractor blade is mounted on the probe.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/261,525 filed on Dec. 1, 2015, the entire disclosureof which is hereby incorporated by reference herein.

BACKGROUND

The lumbar spine refers to the lower back, and is where a human's spinalcolumn curves inward toward the abdomen. The lumbar spine, whichtypically starts five to six inches below the shoulder blades, connectswith the thoracic spine at the top and the sacral spine at the bottom. Ahuman lumbar spine typically includes 5 vertebrae, although someindividuals have six vertebrae in their lumbar spine. There are severaldifferent conditions that can affect the lumbar spine and cause pain,including disk problems. A lumbar spine fusion can be used to helpalleviate pain in some individuals who are suffering from disk problemsand other ailments.

SUMMARY

An illustrative lumbar spine fusion system includes a probe and aretractor blade. The probe includes a shaft, a pointed tip, and acollar. The pointed tip is configured to puncture through the annulus ofthe disk and enter the tissue in a disk space and anchor the probe tothe tissue. The collar is configured to act as a stop to control adistance through which the shaft of the probe traverses the tissue. Theretractor blade includes an end portion and a slot. The slot isconfigured to receive at least a portion of the shaft of the probe. Atleast a portion of the end portion of the retractor blade is configuredto rest upon one or more of the collar and the disk when the retractorblade is mounted on the probe.

An illustrative retractor blade attachment system includes a probe thatincludes a shaft and a pointed tip. The pointed tip is configured topuncture tissue in a disk space of a disk and anchor the probe to thetissue. The system also includes a retractor blade attachment. Theretractor blade attachment includes a slot configured to receive atleast a portion of the shaft of the probe. The retractor bladeattachment also includes one or more connections configured to securethe retractor blade attachment to a retractor blade.

An illustrative method for accessing a spine fusion site includes makingan incision. A probe that includes a shaft and a collar is insertedthrough the incision and into a disk space of a disk such that the probeis anchored to the disk space. The method also includes placing a slotof a retractor blade over at least a portion of the shaft of the probesuch that at least a portion of an end portion of the retractor bladerests upon one or more of the collar and the disk.

The foregoing is a summary of the disclosure and thus by necessitycontains simplifications, generalizations, and omissions of detail.Consequently, those skilled in the art will appreciate that the summaryis illustrative only and is not intended to be in any way limiting.Other aspects, features, and advantages of the devices and/or processesdescribed herein, as defined by the claims, will become apparent in thedetailed description set forth herein and taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a probe in accordance with an illustrative embodiment.

FIG. 2A depicts a retractor blade with a tubular slot and a concave endin accordance with an illustrative embodiment.

FIG. 2B depicts a retractor blade with a tubular slot and a convex endin accordance with an illustrative embodiment.

FIG. 3 is a cross-sectional view of a retractor blade in accordance withan illustrative embodiment.

FIGS. 4A, 4B, 4C, and 4D are cross-sectional views of a retractor bladewith the tubular slot in various configurations, in accordance withillustrative embodiments.

FIG. 5 depicts a retractor blade mounted on a probe in accordance withan illustrative embodiment.

FIG. 6A depicts a retractor blade with an attachment for a handle orretractor system in accordance with an illustrative embodiment.

FIG. 6B is a cross-sectional view of a retractor blade with anattachment for a handle or retractor system in accordance with anillustrative embodiment.

FIG. 7A depicts a shorter retractor blade with a tubular slot, that isdesigned to attach to a longer retractor blade that does not have atubular slot in accordance with an illustrative embodiment.

FIG. 7B depicts a shorter retractor blade with a tubular slot, attachedto a longer retractor blade that does not have a tubular slot inaccordance with an illustrative embodiment.

FIG. 8 is a cross-sectional view of a shorter retractor blade with atubular slot, attached to a longer retractor blade that does not have atubular slot in accordance with an illustrative embodiment.

FIG. 9 depicts a depicts a shorter retractor blade with a tubular slotmounted on a probe, attached to a longer retractor blade that does nothave a tubular slot in accordance with an illustrative embodiment.

FIG. 10 depicts a retractor blade mounted on a probe that has beenanchored in a lumbar vertebral disk, in accordance with an illustrativeembodiment

FIG. 11 is a flow diagram depicting a process for performing a lumbarspine fusion in accordance with an illustrative embodiment.

DETAILED DESCRIPTION

Lateral lumbar spine fusion is typically performed through one or moreincisions placed on the lateral aspect of the abdomen. The incision(s),which are made directly lateral to the vertebral column, are just bigenough to accommodate a table-mounted expandable tubular retractor thatallows visualization of the spine. The spine is approached through theretroperitoneal space. Once the retroperitoneal space is traversed, inorder to visualize the spine, the operative corridor typically involvessplitting the psoas muscle, which sits laterally to the left and rightof the spinal column. This trans-psoas approach endangers the lumbarnerve plexus, which runs through the psoas muscle, and can also causethigh pain due to irritation of the psoas muscle. Neurophysiologicalmonitoring in the form of triggered electromyography (EMG) is used as anadjunct to the trans-psoas approach in order to identify nerves that liewithin or near the surgical corridor so that the chance of nerve injuryis minimized. A probe is typically placed through the psoas muscle andelectrical current is applied via the probe in the standard fashion fortriggered EMG. Provided the surgical corridor is deemed safe by thesurgeon, serial dilators are placed, with triggered EMG performed aftereach dilator placement. Finally, a tubular table-mounted retractor isplaced over the dilators so that the spine can be visualized.

An alternative retroperitoneal surgical technique involves a moreoblique approach to the lumbar spine, working anterior to the psoasmuscles rather than through the psoas muscle. This technique is lessdependent on triggered EMG because the surgical corridor is anterior tothe psoas muscle and the invested lumbar plexus. However, this procedureis a less direct approach to the spine and may endanger the bloodvessels in the area.

Described herein are a system and technique that combine the benefits ofa direct lateral retroperitoneal approach with a surgical corridor thatis anterior to the psoas muscle. Such an approach minimizes oreliminates the need for triggered EMG, and reduces the number of stepsneeded to safely place the retractor. This technique and retractordesign will expedite surgery at levels of the spine where the psoasmuscle can be readily mobilized posteriorly. It will also save cost onsurgeries in which neuromonitoring is not necessary. In addition, thistechnique and retractor can be used for lateral fusion in the thoracicspine, where the psoas muscle and lumbar plexus are not a factor.

One of the difficulties with current state-of-the-art lateral fusionapproaches is the surgeon's ability to hold the dilators in the properposition on the disk space and then deploy the retractor over thedilators. It is common for the dilators to migrate during serialdilation and retractor placement. The technique and retractor heredescribed solves this issue because the probe is anchored into a desiredlocation in the disk space. Once the probe is anchored into the properposition, the retractor can immediately be placed (i.e., without the useof dilators), and will be in the desired position because the probe isalready anchored. Placing the anchor probe as the first step also solvesthe problem of the psoas muscle migrating anteriorly, as commonly occurswhen a dilator is placed without an anchor probe.

Another difficulty with current systems is the use of a deployable shimin the posterior blade of a retractor system that can be deployed intothe disk space to anchor it in place. A concern with deploying this shimis the concern for it causing nerve damage. Instead of using a shim, thetechnique and retractor described herein involves placing the probe intothe disk space under direct visualization, and with the option of usingtriggered EMG if it is thought this will be helpful. This probe thenserves as the anchor over which the retractor is placed. As a result,anchoring the retractor with a device in the disk space is more readilyand more safely accomplished using the embodiments described herein.

The approaches described herein take advantage of the smaller diameterof the psoas muscle and fewer lumbar plexus nerves at the upper lumbarlevels, especially T12-L1, L1-L2, and L2-L3, occasionally L3-L4, andrarely L4-L5. The approaches described herein can also be applied to thethoracic spine, where the psoas muscle is not present. Images such asmagnetic resonance imaging (MM) images or computerized tomography (CT)images are studied to determine the size and location of the psoasmuscle at the desired surgical level, and if it is felt that the anatomyis appropriate, this approach can be used. The present approach isperformed through the same incision or incisions that would be utilizedfor a lateral retroperitoneal approach to the spine.

Once the anterior border of the psoas muscle is identified and the diskspace identified on intra-operative imaging, the psoas muscle iscarefully mobilized posteriorly to identify the disk space. A handheldretractor can be used to carefully retract the psoas muscle in itsentirety posteriorly to further expose the disk space. A probe is thenplaced into the desired location in the disk space based on directvisualization and intra-operative imaging. The desired location istypically located in the posterior ⅓ of the disk space, and will belocated entirely or predominantly anterior to the psoas muscle. Theprobe will hold the psoas muscle posterior to the probe, setting up thelater step of placing the retractor in a position that holds the psoasmuscle entirely or predominantly posterior to the posterior retractorblade.

The lateral approach is designed for use with neuromonitoring, but thisis likely not necessary at the upper lumbar levels because the psoas issmaller in diameter and contains fewer nerves, and the nerves aretherefore less prone to injury. Thus the upper lumbar levels are moreamenable to establishing a surgical corridor anterior to the psoasmuscle. Depending on the individual patient anatomy, it may be possibleto readily establish this corridor, placing the lumbar plexus at minimalrisk. Under these circumstances, neuromonitoring likely does not provideany additional safety to the patient; instead it prolongs the procedureand may make it more complicated and even increase the risk of nerveinjury if the retractor deployment time is prolonged. If the probe andretractor can safely be placed without neuromonitoring, the surgery willbe more expeditious and involve fewer steps, and theoretically decreasethe retractor deployment duration. Serial dilators will not need to beplaced over the probe as is the standard protocol with current laterallumbar fusion techniques. Instead, the retractor in its entirety can beplaced along the probe immediately after the probe is anchored in thedisk space.

FIG. 1 depicts a probe 100 in accordance with an illustrativeembodiment. The probe 100 of FIG. 1 includes a shaft 105 having acircular cross section, and is composed primarily of metal.Alternatively, the probe may have an oval cross-section. A diameter ofthe probe 100 is approximately 2-3 mm, and the probe 100 is fairly rigidso that it can be manipulated manually and so that it can hold aretractor in place once the retractor is placed over the probe 100. Inalternative embodiments, a different diameter of the probe may be used.The probe 100 also includes a collar 110 that is approximately 3-5 mm indiameter, although in alternative embodiments a smaller or largerdiameter may be used. In an illustrative embodiment, the collar 110 islocated approximately 15 cm from an end of the probe, and forms apointed tip 115 of the probe 100 that can be inserted into tissue. Thepointed tip 115 may be slightly blunted in order to avoid inadvertentinjury to structures around the spine. In an alternative embodiment thetip 115 could include fixed or retractable teeth or flanges that wouldhold the probe 100 securely in the disk space. In such an embodiment inwhich the teeth or flanges are extendable and retractable, theextension/retraction can be performed by pushing a button on a handle orother portion of the probe. Upon pushing of the button, theteeth/flanges can be mechanically or electrically controlled, dependingon the implementation. In an alternative embodiment the collar 110 maybe closer to or further from an end of the probe, depending on patient'sanatomy and surgeon preferences. In one embodiment, the collar ispermanently fixed to a location along the shaft of the probe. In analternative embodiment, the collar may be slidably fixed to the shaft ofthe probe. In such an embodiment, the collar may be secured to the probeshaft using a set screw or other fastener such that the collar can beslid to a desired location along the shaft. In an alternativeembodiment, the probe can be designed without a collar.

The collar 110 functions to stop the probe 100 from advancing into thedisk space beyond the collar 110. Specifically, the pointed tip 115 ofthe probe 100 is inserted into the disk space until the collar 110contacts the lateral aspect of the disk and prevents further advancementof the probe 100. In another illustrative embodiment, the probe 100 caninclude an approximately 5 mm area above the collar 110 that is designedto conduct electrical stimulation so that triggered EMG can be employedthrough the probe 100 if desired. However, as discussed above, theembodiments described herein reduce or eliminate the need to usetriggered EMG.

Once the probe 100 is anchored in the disk space and the appropriateposition confirmed with direct visualization and via intra-operativeimaging, a retractor blade with a circular or oval tube designed toaccommodate and contain the probe is placed over the probe and slid downthe probe onto the disk space. The psoas muscle is held posterior to theretractor blade, and the retractor blade is held in position by theprobe that is itself anchored into the disk space. This retractor bladewill typically be part of an expandable table-mounted retractor systemthat has a total of 2, 3 or 4 blades. The posterior blade is attached tothe retractor system and then advanced along the probe, such that theprobe, by nature of being anchored into the disk space and beingcontained within a tube in the retractor blade, holds the retractor inposition. The retractor is therefore located anterior to the psoasmuscle and holds the psoas muscle in position, thereby preventing itfrom migrating in an anterior direction. The table-mounted retractor isthen secured to the operative table to lock it in position, the bladesof the retractor are expanded to the desired diameter, and the spinalfusion proceeds in the standard manner. In alternative embodiment, theretractor blade can be used independently, without a table-mountedretractor system.

FIG. 2A depicts a retractor blade 200 with a tubular slot 205 and aconcave end 210 in accordance with an illustrative embodiment. FIG. 2Bdepicts a retractor blade 250 with a tubular slot 255 and a convex end260 in accordance with an illustrative embodiment. In alternativeembodiments, the slots 205 and 255 may take on a shape other thantubular, such as triangular, square, etc. The tip of the retractor bladecontacts and rests on the lateral aspect of the disk, and can be convexin nature as illustrated in FIG. 2B. Alternatively, the tip of theposterior retractor bade can be concave in shape with a variable radiusof curvature to best accommodate the convex shape of the lateral aspectof the disk, as illustrated in FIG. 2A. In the embodiment of FIG. 2A,the concave end 210 of the retractor blade 200 would thus follow theshape of the disk and vertebral bodies, thereby preventing the psoasmuscle from slipping underneath the corners of the retractor blade ascan occur when the distal end of the retractor blade has a convex shape.The retractor blades described herein can be designed to be used withcurrently existing table-mounted retractors, or they can be part of awhole new table-mounted retractor design, or they can functionindependent of a table-mounted retractor system. The tip of theretractor blade can be flat rather than concave or convex.

FIG. 3 is a cross-sectional view of a retractor blade 300 in accordancewith an illustrative embodiment. As illustrated in FIG. 2 and FIG. 3, atubular slot 305 of the retractor blade 300 is positioned in-line with awall of the retractor blade 300. Alternatively, the tubular slot 305 maybe positioned at least partially internal to or external to the wall ofthe retractor blade.

FIG. 4A is a cross sectional view of a retractor blade 400 in accordancewith an illustrative embodiment. A tubular slot 405 is positionedeccentrically so that it is partially posterior to the retractor blade400. Alternatively, the tubular slot may be positioned entirelyposterior to the retractor blade.

FIG. 4B is a cross sectional view of a retractor blade 420 in accordancewith an illustrative embodiment. A tubular slot 425 is positionedeccentrically so that it is partially anterior to the retractor blade420.

FIG. 4C is a cross sectional view of a retractor blade 440 in accordancewith an illustrative embodiment. A tubular slot 445 is positionedentirely anterior to the retractor blade 440.

FIG. 4D is a cross sectional view of a retractor blade 460 in accordancewith an illustrative embodiment. A tubular slot 465 is positionedeccentrically so that it is partially anterior to the retractor blade,and the tubular slot 465 is partially open, unlike the embodiments inFIGS. 4A-4C. In alternative embodiments, any of the tubular slots 405,425, and 445 of FIGS. 4A-4C may be partially open which would decreaseits profile and facilitate cleaning the retractor blade slot aftersurgery

FIG. 5 depicts a retractor blade 520 mounted on a probe 500 inaccordance with an illustrative embodiment. Specifically, a tubular slot525 of the retractor blade 520 is mounted onto a shaft 505 of the probe500. A collar 510 of the probe 500 acts as a stop upon which a portionof an end of the retractor blade 520 rests. The collar 510 of the probe500 also acts as a stop for insertion of a pointed tip 525 of the probe500 into tissue. Specifically, the collar 510 controls a depth at whichthe probe 500 can be inserted into the tissue. In the embodiment of FIG.5, the retractor blade 520 includes a convex end adjacent to the collar510. As discussed above, in alternative embodiments, the end of theretractor blade may be concave such that the retractor blade better fitsthe contour of the disk upon which the retractor blade rests. It is alsopossible for the probe to not have a collar, in which case the tip ofthe retractor blade would contact the disk in its entirety rather thatthe collar.

FIG. 6A depicts a retractor blade 620 with a tubular slot 625 asdescribed and referenced in FIG. 2B, with an attachment 630 designed toaccommodate a handle that connects to the attachment 630 through anopening 635 in accordance with an illustrative embodiment. The opening635 can be a threaded screw hole configured to receive a screw.Alternatively, the opening 635 can be configured to receive otherattachment mechanisms such as a bolt, pin, clip, etc., and the opening635 may be threaded or unthreaded depending on the embodiment. Inanother alternative embodiment, opening 635 can be used to secure theretractor blade 620 to an expandable retractor system.

FIG. 6B is a cross sectional view of a retractor blade 620 with atubular slot 625 and an attachment 630 designed to connect to a handleor to an expandable retractor system through an opening 635. Similar tothe embodiment of FIG. 6A, the opening 635 may be threaded orunthreaded, and can be configured to receive any of a number ofdifferent attachment mechanisms.

FIG. 7A depicts a retractor blade 700 that does not have a tubular slot,but that slides into and connects to a retractor blade attachment 750that has a tubular slot 760 in accordance with an illustrativeembodiment. Retractor blade 700 attaches to retractor blade attachment750 through connections 765, 770, 775, and 780, as depicted in FIG. 7B.In this embodiment, an existing retractor blade system that does nothave a tubular slot can be used with retractor blade attachment 755 suchthat a probe as depicted in FIG. 1 is docked in the disk space and thenthe retractor blade 700 connected to retractor blade attachment 755 isslid along the probe through the tubular slot 760. The connections 765,770, 775, and 780 are slotted clips that receive edges of the retractorblade 700 and hold the retractor blade 700 in place via a friction fit.In an alternative embodiment, retractor blade 700 can be joined toretractor blade attachment 750 through connection points other than 765,770, 775, and 780. For example, fewer or additional connection pointsmay be used. Also, other types of connections may be used, such asscrew(s), bolt(s), spring loaded clips, detachable clips, etc.

FIG. 8 is a cross-sectional view of a retractor blade 700 secured to aretractor blade attachment 750 through connections 765 and 775.Retractor blade attachment 750 has a tubular slot 760. FIG. 8 is across-sectional view of FIG. 7B.

FIG. 9 depicts a retractor blade 925 connected to a retractor bladeattachment 950, with the retractor blade attachment 950 having a tubularslot 980 that accommodates a probe 900 in accordance with anillustrative embodiment. The retractor blade 925 is secured to theretractor blade attachment 950 through connections points 955, 960, 965,and 970.

FIG. 10 depicts a retractor blade 1020 with a tubular slot 1025, a probe1000, and a vertebral segment 1040 in accordance with an illustrativeembodiment. The standard lateral retroperitoneal approach is performed,and the psoas muscle identified and mobilized posteriorly. The probe1000 has a pointed tip 1010 and is inserted and docked in theintervertebral disk 1060. The intervertebral disk 1060 is locatedbetween vertebral bodies 1050 and 1055 and these three structurescomprise the vertebral segment 1040. The probe 1000 has a collar 1005that is flush with the lateral aspect of the intervertebral disk 1060.The collar 1005 controls the depth of probe insertion by coming intocontact with the disk and preventing further probe advancement, and alsoallows for fluoroscopic or other intra-operative imaging determinationof probe location with respect to the disk 1060. Once the probe 1000 isdocked in the disk 1060 in the desired location based on directvisualization and fluoroscopic or other intra-operative imaging, theretractor blade 1020 is placed onto probe 1000 via tubular slot 1025which accommodates probe 1000, and the retractor blade 1020 is slid downthe probe 1000 until the leading edge of the retractor blade 1020 comesinto contact with the intervertebral disk 1060 and adjacent vertebralbodies 1050 and 1055. The probe 1000 is contained within the tubularslot 1025 and thus serves to both guide the retractor blade 1020 intothe desired position and then to hold the retractor blade 1020 in thisposition by virtue of being anchored in the intervertebral disk 1060.The retractor blade may be optionally attached to a table-mountedexpandable tubular retractor, and then the fusion proceeds in thestandard manner.

FIG. 11 is a flow diagram depicting a process for performing a lumbarspine fusion in accordance with an illustrative embodiment. Inalternative embodiments, fewer, additional, and/or different operationsmay be performed. Additionally, the use of a flow diagram is not meantto be limiting with respect to the order of operations performed. In anoperation 1100, the surgeon determines an incision location. In anillustrative embodiment, the incision location is determined with theuse of fluoroscopy. Alternatively, any other method(s) known to those ofskill in the art may be used. In an operation 1105, the surgeon makes anincision at the determined incision location.

In an operation 1110, the surgeon accesses and manually retracts thepsoas muscle. As discussed herein, once the anterior border of the psoasmuscle is identified visually, the psoas muscle is carefully mobilizedposteriorly to reveal the disk space. Once the disk is identified, ahandheld retractor can be used to carefully retract the psoas muscle inits entirety posteriorly to further expose the disk. In an operation1115, a probe is inserted into and thus anchored in the disk space. Inan illustrative embodiment, the probe is the probe 100 described withreference to FIG. 1.

In an operation 1120, the surgeon mounts a posterior blade of aretractor onto the anchored probe. In an illustrative embodiment, theposterior blade of the retractor includes a slot that is configured toreceive a portion of a shaft of the probe, as illustrated and describedwith reference to FIG. 5. As noted above, another portion of the shaftof the probe is already anchored into the disk space. In an operation1125, the surgeon completes the fusion procedure as known to those ofskill in the art.

The components described herein can be made in a variety of lengthsand/or shapes to accommodate various patient anatomies and surgeonpreferences. The components can be made from stainless steel, titanium,titanium-alloy, cobalt-chrome, or any suitable material that is able towithstand the biomechanical stresses under which they will be placed.

The foregoing description of illustrative embodiments has been presentedfor purposes of illustration and of description. It is not intended tobe exhaustive or limiting with respect to the precise form disclosed,and modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the disclosed embodiments.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. A lumbar spine fusion system comprising: a probethat includes a shaft, a pointed tip, and a collar, wherein pointed tipis configured to puncture tissue in a disk space of a disk and anchorthe probe to the tissue, and wherein the collar is configured to act asa stop to control a distance through which the shaft of the probetraverses the tissue; and a retractor blade that includes an end portionand a slot, wherein the slot is configured to receive at least a portionof the shaft of the probe, and wherein at least a portion of the endportion is configured to rest upon one or more of the collar and thedisk when the retractor blade is mounted on the probe.
 2. The lumbarspine fusion system of claim 1, further comprising a fastener configuredto secure the collar to the shaft such that the collar is slidablymounted to the shaft.
 3. The lumbar spine fusion system of claim 1,wherein the end portion of the retractor blade is convex.
 4. The lumbarspine fusion system of claim 1, wherein the end portion of the retractorblade is concave.
 5. The lumbar spine fusion system of claim 1, whereinthe slot of the retractor blade is a tubular slot, and wherein thetubular slot is positioned within a wall of the retractor blade.
 6. Thelumbar spine fusion system of claim 1, wherein the slot of the retractorblade is positioned partially or completely anterior to the retractorblade.
 7. The lumbar spine fusion system of claim 1, wherein the slot ofthe retractor blade is positioned partially or completely posterior tothe retractor blade.
 8. The lumbar spine fusion system of claim 1,wherein the slot of the retractor blade is a partially open slot.
 9. Aretractor blade attachment system comprising: a probe that includes ashaft and a pointed tip, wherein pointed tip is configured to puncturetissue in a disk space of a disk and anchor the probe to the tissue; anda retractor blade attachment, wherein the retractor blade attachmentincludes a slot configured to receive at least a portion of the shaft ofthe probe; and one or more connections configured to secure theretractor blade attachment to a retractor blade.
 10. The retractor bladeattachment system of claim 9, further comprising a collar on the probe,wherein the collar is configured to act as a stop to control a distancethrough which the shaft of the probe traverses the tissue.
 11. Theretractor blade attachment system of claim 10, wherein the retractorblade attachment further comprises an end portion, and wherein at leasta portion of the end portion is configured to rest upon one or more ofthe collar and the disk when the retractor blade attachment is mountedon the probe.
 12. The retractor blade attachment system of claim 10,further comprising a fastener configured to secure the collar to theshaft such that the collar is slidably mounted to the shaft.
 13. Theretractor blade attachment system of claim 9, wherein the one or moreconnections comprise one or more clips configured to secure one or moreedges of the retractor blade.
 14. The retractor blade attachment systemof claim 9, wherein the slot of the retractor blade attachment is atubular slot, and wherein the tubular slot is positioned within a wallof the retractor blade attachment.
 15. The retractor blade attachmentsystem of claim 9, wherein the slot of the retractor blade attachment isa partially open slot.
 16. A method for accessing a spine fusion site,the method comprising: making an incision; inserting a probe thatincludes a shaft and a collar through the incision and into a disk spaceof a disk such that the probe is anchored to the disk space; and placinga slot of a retractor blade over at least a portion of the shaft of theprobe such that at least a portion of an end portion of the retractorblade rests upon one or more of the collar and the disk.
 17. The methodof claim 16, wherein said inserting comprises inserting the probe untilat least a portion of the collar of the probe contacts a wall of thedisk space.
 18. The method of claim 16, further comprising slidablymounting the collar onto the shaft of the probe.
 19. The method of claim16, wherein the end portion of the retractor blade is concave or convex.20. The method of claim 16, wherein the slot of the retractor blade ismounted at least partially posterior or at least partially anterior tothe retractor blade.